Conventionally, delay blasting methods using a delay detonator have been most advantageously employed to reduce ground vibration or noise effectively upon blasting. As methods for reducing ground vibration or noise more effectively, Japanese Patent Publication No. 122559/1995, Japanese Patent Application Laid-Open No. 285800/1989 and the like have proposed blasting methods using a detonator excellent in time accuracy which is controlled by integrated circuits, wherein dominant frequency or a waveform generated by a test single-hole blast is preliminarily monitored at a location where the ground vibration or noise becomes problematical and initiation intervals for a delay blast are determined based on the above-monitored dominant frequency or waveforms.
The waveforms of the ground vibration or noise generated by a blast are greatly influenced by the type of a target rock. In order to reduce ground vibration or noise generated by blasting a target rock most effectively according to the above methods, it is necessary to monitor dominant frequency or waveform of ground vibration or noise which is generated by a test single-hole blast at problematic locations every time before blasting a target rock.
Therefore, it is difficult to minimize ground vibration or noise constantly according to the conventional methods.